Recently, driven by the energy crisis and the heightened awareness of environmental protection, the European Union, North America, and Japan have passed green laws and regulations regarding electronic equipment which not only regulate the conversion efficiency of such equipment but also impose stringent requirements on no-load or standby power consumption. In a conventional alternating current to direct current (AC-to-DC) converter, as shown in FIG. 1, an electromagnetic interference (EMI) filter 10 includes a capacitor Cx whose two ends a. and b are connected to an AC power source VAC, a bridge rectifier 12 rectifies the voltage Vx across the capacitor Cx to produces an input voltage VIN, and a power supply 14 converts the input voltage VIN into an output voltage VOUT. When the AC power source VAC is removed, the voltage Vx across the capacitor Cx can be as high as hundreds of volts. In order to prevent electric shock, a bleeding resistor R1 is connected in parallel to the capacitor Cx to establish a discharge path for discharging the capacitor Cx after the AC power source VAC is removed. However, in the course where the AC power source VAC continuously supplies electricity, a current keeps flowing through the bleeding resistor R1 and thus causes extra power consumption. Under currently applicable safety regulations, for example CEI/IEC 60950-1 Clause 2.1.1.7, the discharge time constant R1×Cx established by the capacitor Cx and the bleeding resistor R1 is required to be less than one second. Therefore, the higher the capacitance Cx is, the lower the resistance R1 must be, and the lower the resistance R1, the higher the power consumption caused thereby. Especially, when the system is in a standby mode, the power consumed by the bleeding resistor R1 accounts for a considerable proportion of the total no-load power consumption.